The present invention relates to molding machines, and in particular to molding machines of the type having movable die halves with means for injecting a liquid or soft molding material therein, such as those used in die casting, injection molding, and the like.
Molding machines are used to form a wide variety of articles from different types of materials, such as metal, plastics, and the like. Although the present invention is particularly adapted for forming metal parts by die casting, it is to be understood that other molding machines and processes encounter problems similar to those experienced in die casting. Hence, the novel features and arrangements of parts disclosed and claimed herein are to be considered equally applicable to such alternative molding devices.
One problem associated with molding machines in general, and in particular with die casting machines, relates to the degree of difficulty and amount of time which is required to remove and replace dies from the machine. Large die casting machines for deep castings, such as those used to form engine blocks and other large parts, typically require a great deal of time and effort to remove and replace the dies, and further require the services of highly skilled workers from a wide variety of trades, including millwrights, electricians, and plumbers. Heretofore, the utility services for the dies, such as plumbing for hydraulics and cooling water, wiring for electrical controls, and the like, have been hooked up after the die is positioned in the molding machine. These utility connections alone result in substantial down time for the machine. Not only is machine down time extremely costly from the standpoint of overhead, but die changeover must usually be performed on a premium time basis, thereby causing high labor costs. Since die removal and replacement must be accomplished in accordance with a set sequence or procedure, the various skilled trades must be scheduled to work on the die in overlapping shifts, and/or simultaneous jobs, thereby creating an inherently inefficient operation. Another problem experienced with die casting machines stems from the manner in which the die halves are mounted on the platens. Typically, the die halves are suspended adjacent to the platens, and then fastened thereto so that the die halves project from the platens in a cantilevered fashion. This arrangement makes it quite difficult to achieve proper initial alignment of the die halves. Also, as the die halves are heated up and cooled during operation, thermal expansion and contraction causes the die halves to move out of alignment, such that frequent adjustment is often necessary. In a similar manner, the various parts of the molding machines, such as the platens and the toggles, are typically positively connected with a common base member during operation, such that uneven thermal expansion, and the intermittent forces of die injection tend to loosen these connections and shift the molding machine members out of alignment.
Yet another problem experienced with die casting is the secure sealing of the die halves together in the closed position. If the die halves are not properly sealed, molten metal will "spit" from the die, thereby creating a substantial safety hazard, and often injuriously effecting the formation of the molded article. This problem is particularly apparent in large die casting machines, which have dies with large surface areas and/or complex shapes, thereby requiring very high injection pressures.
Still another problem associated with large die casting machines, such as those noted hereinabove, is that the same are extremely heavy and massive, thereby creating serious shipping problems. Heretofore, even special shipping procedures have required that the machines be disassembled to a considerable extent, such that extensive reassembling, setup, and readjustment is required before the machine can be placed in initial operation.